Influencing Factors of Failure Modes in High-Speed Permanent Magnet Motor Rotors Under Axial Constraint

High-speed permanent magnet machines frequently employ axially constrained solid rotors. These rotors undergo complex failure due to the combined action of centrifugal loading and interference-fit contact pressure. Existing analytical models often overlook this interaction, which can lead to overestimated reliability. To address this limitation, a three-dimensional axisymmetric elastic–static model is developed. This model quantifies how rotational speed and interference fit jointly govern failure behaviour. A systematic computational framework is established to evaluate three primary failure modes: interface debonding, permanent magnet fracture, and retaining sleeve yielding. The framework explicitly accounts for axial constraint effects. Finite element simulations and prototype testing on a 3 kW, 200,000 r/min motor validate the model, confirming its accuracy in predicting failure limits. The stress distributions and dynamic responses under axial constraint are systematically analysed and compared with numerical and experimental results. Consequently, the proposed approach provides a reliable foundation for designing high-speed rotors under axial constraints.